Comet of the CenturyPBS launches an evening of space related programs with a look at the fast approaching comet ISON. 7 and 10 p.m. KOCE That's followed at 8 and 9 p.m. by episodes of "Nova" that look at the boundary between the upper atmosphere and space, and the threat (and potential benefits) of asteroids.

Revolution Charlie (Tracy Spiridakos) tries to show Rachel (Elizabeth Mitchell) how much she's grown and Neville (Giancarlo Esposito) makes a proclamation to Jason (JD Pardo) in this new episode. 8 p.m. NBC

Arrow Oliver (Stephen Amell) investigates when a mysterious illness is infecting hundreds of people in the city, including Diggle (David Ramsey) in this new episode. 8 p.m. KTLA